1. Field of the Invention
The present invention relates to a coding and decoding system for wireless telecommunication by means of using a wireless telecommunication device and a personal card attached thereto.
2. Description of the Prior Art
According to the increase in commerce on wireless telecommunication, consumers are apt to be gotten into trouble. Using coding techniques on wireless telecommunication prevents the influence of noises and invaders. However, it is difficult to keep the communication secret by the coding technique based on conventional hard-wears such as magnetic cards and IC cards. The magnetic cards are very convenient and popular, however it is easy to make copies thereof or steal passwords. Therefore, damages by unlawful using of credit cards, cash cards, prepaid cards, and so on are increasing year after year. The IC cards are superior to the magnetic cards in difficulty in counterfeiting of cards, however it is not enough to keep the communication secret thoroughly. Thus, conventional hard-wears have problems on keeping a communication security.
An object of the present invention is to provide a personal card useful as credit card, cash card, key, and others.
Another object of the present invention is to provide a personal card excellent in difficulty in counterfeiting and stealing of passwords.
Another object of the present invention is to provide a coding and decoding system for wireless telecommunication capable of recognizing the personal-card singularity in secret.
Another object of the present invention is to provide a coding and decoding system for wireless telecommunication capable of keeping a network communication secret.
Another object of the present invention is to provide a coding and decoding system for wireless telecommunication capable of low electric power consumption.
Another object of the present invention is to provide a coding and decoding system for wireless telecommunication excellent in durability and manufacturing.
A still other object of the present invention is to provide a coding and decoding system for wireless telecommunication having a small size and a simple structure.
According to one aspect of the present invention there is provided a coding and decoding system for wireless telecommunication comprising a wireless telecommunication device and a personal card attached thereto. The wireless telecommunication device consists of a first piezoelectric substrate, a coded IDT, a first electrode-group, a first amplifier, an antenna, a second amplifier, a second electrode-group, a first intermediary IDT, and a signal analyzer. The personal card consists of a second piezoelectric substrate, a personal coded IDT, a third electrode-group, a second intermediary IDT. The coded IDT consists of interdigital electrode pairs Pi (i=1, 2, . . . , n), of which two neighbors are at a distance L from each other, and having a coded pattern. The first electrode-group consists of an interdigital electrode A0 and an interdigital electrode Ai (i=1) at a distance iL (i=1) from the interdigital electrode A0. The second electrode-group consists of a central interdigital electrode B0, a right interdigital electrode Bxe2x88x921 at a distance L0 from the central interdigital electrode B0, and a left interdigital electrode Bi (i=1) at a distance L0+iL (i=1) from the central interdigital electrode B0. The personal coded IDT includes the interdigital electrode pairs Pi, and has a personal coded pattern. The third electrode-group consists of an interdigital electrode C0 and an interdigital electrode Ci (i=1) at the distance iL (i=1) from the interdigital electrode C0.
The coding and decoding system for wireless telecommunication has four sections, that is, (1) a personal transmitting section composed of the second piezoelectric substrate, the personal coded IDT, the third electrode-group, the first amplifier, and the antenna; (2) a main transmitting section composed of the first piezoelectric substrate, the coded IDT, the first electrode-group, the first amplifier, and the antenna; (3) a personal receiving section composed of the antenna, the second amplifier, the first piezoelectric substrate, the second electrode-group, the second piezoelectric substrate, the second intermediary IDT, the personal coded IDT, and the signal analyzer; and (4) a main receiving section composed of the antenna, the second amplifier, the first piezoelectric substrate, the second electrode-group, the first intermediary IDT, the coded IDT, and the signal analyzer.
In the personal transmitting section, when a pulse (1) is applied to the personal coded IDT, a personal coded SAW corresponding to the personal coded pattern is excited on the second piezoelectric substrate. The personal coded SAW is detected as a personal coded burst-signal at the interdigital electrode C0, and after a time corresponding to the distance L, at the interdigital electrode C1 again. The personal coded burst-signals at interdigital electrodes C0 and C1 form a personal double-coded burst-signal, which is emitted from the antenna via the first amplifier.
In the main transmitting section, when a transmitting-message digital-signal is applied to the coded IDT, a coded SAW is excited on the first piezoelectric substrate. The coded SAW corresponding to the coded pattern is detected as a coded burst-signal at the interdigital electrode A0, and after a time corresponding to the distance L, at the interdigital electrode A1 again. The coded burst-signals at the interdigital electrodes A0 and A1 form a double-coded burst-signal, which is emitted from the antenna via the first amplifier.
In the personal receiving section, if a private double-coded burst-signal is caught at the antenna, it is applied to right interdigital electrode Bxe2x88x921 and left interdigital electrode B1, respectively, via the second amplifier. In this time, first- and second SAWs are excited on the first piezoelectric substrate, respectively. The first SAW arrives at the central interdigital electrode B0 by a time corresponding to the distance L before the second SAW arrives at the central interdigital electrode B0. As a result, the private double-coded burst-signal is converted into a private mono-coded burst-signal at the central interdigital electrode B0. When the private mono-coded burst-signal is applied to the second intermediary IDT 16, a private mono-coded SAW along the reverse direction to the personal coded SAW in the personal transmitting section is excited on the second piezoelectric substrate. If the private mono-coded SAW correlates to the personal coded pattern, a private decoded pulse is detected at the personal coded IDT. The private decoded pulse is received at the signal analyzer.
In the main receiving section, if a receiving-message double-coded burst-signal is caught at the antenna, it is applied to right interdigital electrode Bxe2x88x921 and left interdigital electrode B1, respectively, via the second amplifier. In this time, third- and fourth SAWs are excited on the first piezoelectric substrate, respectively. The third SAW arrives at the central interdigital electrode B0 by a time corresponding to the distance L before the fourth SAW arrives at the central interdigital electrode B0. As a result, the receiving-message double-coded burst-signal is converted into a receiving-message mono-coded burst-signal at the central interdigital electrode B0. When the receiving-message mono-coded burst-signal is applied to the first intermediary IDT, a mono-coded SAW along the reverse direction to the coded SAW in the main transmitting section is excited on the first piezoelectric substrate. If the mono-coded SAW correlates to the coded pattern, a decoded pulse is detected at the coded IDT. The decoded pulse is received at the signal analyzer.
According to another aspect of the present invention there is provided a coded IDT consisting of at least three interdigital electrode pairs.
According to another aspect of the present invention there is provided a personal coded IDT comprising a row of multiple times four blocks, of which at least one has the same construction as the coded IDT and all the others have no-electrode-pair constructions with the same outward size as the coded IDT.
According to other aspect of the present invention there are provided first-, second-, and third electrode-groups. The first electrode-group includes at least two interdigital electrodes Ai {i=1, 2, . . . , (nxe2x88x921)} at a distance iL {i=1, 2, . . . , (nxe2x88x921)}, respectively, from the interdigital electrode A0. The second electrode-group includes at least two left interdigital electrodes Bi {i=1, 2, . . . , (nxe2x88x921)} at a distance L0+iL {i=1, 2, . . . , (nxe2x88x921)}, respectively, from the central interdigital electrode B0. The third electrode-group includes at least two interdigital electrodes Ci {i=1, 2, . . . , (nxe2x88x921)} at a distance iL {i=1, 2, . . . , (nxe2x88x921)}, respectively, from the interdigital electrode C0.
According to a further aspect of the present invention there are provided a bipolar-pulse generator, and first- and second coded IDTs in place of the coded IDT.